正则表达式匹配的模式匹配

Question

The official tutorial ( https://www.python.org/dev/peps/pep-0636/#adding-a-ui-matching-objects ) shows that you can use use objects with the new pattern matching syntax, so I wanted to use it with regex matches like this:

import re

match re.match(r"^foo", "foobar"):
    case re.Match(span=(start, end), match=match):
        print(f"match: {match} ({start}-{end})")
    case _:
        print("no matches")

But the first case never executes, what am I doing wrong?

Answer 1

Use a wrapper to wrap the args you want, or even if you just want a non-none match, you can do that here.

 import re


class MatchWrap:
    __match_args__ = "string"

    def __init__(self, string, match: None):
        self.string = string
        self.match = match


def wrap_match(match):
    if match:
        return MatchWrap(match.string, match)
    else:
        return None


match wrap_match(re.match(r"^foo", "foobar")):
    case MatchWrap(string="foobar") as obj:
        print(f"match: {obj.match.string} ({obj.match.start}-{obj.match.end})")
    case _:
        print("no matches")